1. Field of the Invention
This invention relates to a monitoring system using an infrared monitoring camera and image processing and, more particularly to detecting either trouble in a facility or the presence of an unexpected person through an unusual temperature rise.
2. Description of the Related Art
Burglar alarm systems have generally employed a video camera system or a light beam sensor system in order to detect an invader. In a video camera system either a watchman has to constantly monitor a display screen or an electronic circuit has to be employed to detect and recognize a change in the video signals. In a light beam sensor system, a beam of invisible light, typically infrared, is projected through the area to be watched. When an invader interrupts the light beam, the presence of the invader is electronically detected. In a facility trouble-finding system, where trouble is typically represented as an abnormal temperature rise of a facility, a contact-type sensor, typically a thermometer, is attached on some part of the facility or a non-contact type infrared detector or camera is employed.
These conventional systems have the following problems. In a system using a video camera, it is impossible for a human to pay constant and perfect attention to the display screen. Therefore, data processing techniques have been employed to electronically detect a change in video information, such as brightness or color. Data processing techniques have also been employed in infrared camera systems to detect a change in temperature of each picture element. Such a system is disclosed in Japanese unexamined patent publication Sho 62-111588.
However, these electronic detection systems detect even a slight change in the object scene, such as a small vibration of a tree, an invasion of a small animal, or a flying leaf. As a result of these undesired detections, the dependability of these conventional systems is low. In order to decrease the excessive sensitivity of systems using a video camera detecting visible light, a system was proposed such that an alarm signal was output only when the quantity of picture elements which have changed more than a predetermined information difference exceeded a predetermined threshold quantity. Such a video camera system is disclosed in the Japanese unexamined patent publication Sho 57-160282.
Moreover, in some temperature measurement systems using a contact-type thermometer, the thermometer needs to be installed on a dangerous part of the facility, such as on a high voltage machine. Accordingly, the installation of the contact-type thermometer is sometimes impossible. An infrared thermometer can be used in place of the contact-type thermometer as a remote sensor. However, in either case, when an infrared thermometer or the contact-type thermometer is used for detecting a temperature rise of the facility, the monitoring is limited to only a part of the facility, neither are suitable to monitor a wide area of a facility.
Furthermore, in a conventional video detection system, a signal generated by detecting a significant change in the object scene is used to actuate an alarm system, to trigger a memory device to later output stored information, or to initiate a video tape recorder and so on. However, in these systems there remains the problem that once the trigger signal is output, the scene prior to the trigger signal cannot be reproduced.